Pulse generating system



S- 5, 1947- E. M. OSTLUND ET AL PULSE GENERATING SYSTEM Filed llarch l3, 1943 4 Sheets-Sheet 1 Aug. 5, 1947. osTLuN ET AL PULSE sxusaumq SYSTEM Filed March 13, 1943 4 Sheets-Sheet 2 I N V EN TORS [VERT MflNl/IL can wvo mm. 091 30x0: or!

Byg7/jjztrifi g- 5, 1947' E. M. OSTLUND ET AL 2,424,999

YULSE GENERATING SYSTEM Filed March 13, 1943 4 Sheets-Shoot 3 P/IUL M 8 BY/ *7 0 m mm L m W Filed March 13, 1943 4 shuts-shut 4 INVENTOIB IYER'T Man/an osnuuo w. aokoLaFr I Patented Aug. 5,1947

PULSE GENERATING SYSTEM Evert Manuel Ostlund, Montclalr, N. J., and Paul W. Sokolofl, Forest Hills, N. Y., assignors to Federal Telephone and Radio Corporation, Newark, N. 1., a corporation of Delaware Application March 13, 1943, Serial No. 479,012'

This invention relates to pulse generating systems and more particularly to the generation of pulses for synchronizing and other purposes.

One of the objects of this invention is to generate low and/or high potential synchronizing pulses from a relatively low voltage sourceof alternating current wherein the pulses are consistently reproducible in substantially a predetermined phase relation with respect to the source of alternating current.

Another object of the invention is to provide in addition to a high potential pulse a high speed sweep potential in a desired time relation with respect to the occurrence of the high potential pulse.

Still another object of the invention is to provide a high potential pulse and a low potential pulse together with a sweep potential wherein the phase relation of the low potential pulse and the sweep potential may be controlled with respect to the dis charge of the high potential pulse.

The production of an initial pulse from an alternating current source is accomplished according to our invention by applying alternating voltage in a particular phase relationship tolthe electrodes of a gas-discharge tube. The voltage applied to the grid, for example, is shifted in phase so as to provide a bias in phase opposition to the anode voltage. Control of the conduction of the tube may be accomplished by controlling the phase shift of the potential applied to the grid, or by amplitude control with a fixed phase shift. When the phase shifted voltage on the grid overcomes the critical negative grid bias, conduction i initiated thereby producing a sudv den flow of current through the tube resulting in a sharpincrease in potential at the cathode of the tube thereby defining a substantially vertical leading edge for the pulse. The trailing edge of the pulse is controlled by decrease of the anode voltage. The phase shifted voltage is such that the discharge through the tube is caused to occur in the desired portion of a half cycle of the altern ating current supply, ,and where two tubes are used in push-pull relation, pulses are produced one for each of the first and second halves of the cycle. These pulses may be differentiated to produce narrow pulsations substantiallyboincident with the leading edges of the pulses and used as low voltage synchronizing pulses. The

7 Claims. (Cl. 250-127) supplying condenser or other source.

pulse output of the tubes may also be shaped by an integration circuit so that the leading edge thereof can be used as a high speed synchronized sweep potential.

The high potential pulses are produced by providing a supply of energy either in the form of momentarily condenser-stored alternating current or stored direct current. The energy storing or supplying condenser is connected through a suitable circuit with the anode of an electron tube which is controlled by the aforementioned low voltage synchronizing pulsations. The anode circuit of the electron tube may include the primary of a transformer so that when the tube is triggered by a pulsation the stored energy is discharged through the primary of the transformer thereby producing a high potential in the sec-,

ondary thereof. The duration of the conduction may be controlled so that the secondary output constitutes a high potential pulse of short dura-' tion. Other arrangements may be provided to produce the high potential pulse such as'by apower amplifier tube controlled by the pulsations. The anode ofthis tube is connected to the energy gering operation is similar as above-described except that in place of a transformer a load resistor is connected between the energy storing condenser and ground. In either arrangement the power required to provide a cut-off biasfor the electron tube whatever its characteristics might be may be supplied from either a rectifier or a transformer.

In many instances, it is desirable to provide low voltage pulses or sweep potentials in association with a high potential pulse. For example, they may be useful for blocking purposes as in the case of radio detection apparatus where it is desirable to block receiver equipment during the transmission of a high potential impulse. Thus, the output of low voltage pulses and the initiation of the sweep potential, may be arranged to lead or lagthe discharge of the high potential synchronizing pulses. The high potential pulse is particularly useful for synchronizing Purposes such as where high peak voltages of 3,000 volts more or less across say a resistor of 25,000 ohms load are required. As a specific example, the high potential pulses produced by this inventionare especially useful for synchronizing a 15,000 volt The trig 100 kilowatt peak power output of a modulator such as disclosed in the copending application of Labin-Ostlund, Serial No. 475,738, filed February 13, 1943.

for a further understanding of the invention, reference may be had to the following detailed description to be read in connection with the accompanying drawings, in which:

Fig. l is a schematic wiring diagram of the pulse generating system according to this invention;

Fig. 2 is a graphical illustration of the operating features of the system in Fig. 1;

Fig. 3 is a schematic wiring diagram of a second embodiment of the invention;

Fig. 4 is a schematic wiring diagram of a third embodiment, and

Fig. 5 is a graphical illustration of the operating of the embodiment in Fig. 4.

Referring to Figs. 1 and 2, the pulses l8 initially generated by the system are produced by a circuit comprising two gas-discharge tubes ll, l2 and a transformer iii to which is coupled a source of alternating current is preferably sinusoidal as indicated by the voltage 32 of curve a. The secondary ll of the transformer is connected in push-pull relation by connections l6 and 18 to the anodes l1 and i8 of the tubes II and I2. The circuit connections between the two tubes and the secondary H are identical so that only the connections to the tube I I need be discussed. Interposed between the connection l8 and a midground tap 28 on the secondary i8 is a condenser 2i. Two resistors R1 and R2 are provided between the connection l8 and a ground lead 28 which is connected to the tap 28. Likewise, resistors R3 and R4 are connected between the ground lead 24 and the opposite connection i8. The resistors R1, R3 are preferably of considerably larger value than the resistors R: and R4.

To provide proper grid control of the tube H, the grid 28 is connected by isolating resistor 25 through an attenuating and phase shifting network comprising a variable resistor 21 and a condenser 28 to an adjustable contact 28 on the opposed phase resistor R4. As shown at a in Fig. 2, this provides an attenuated biasing potential 38 on the grid 26 which is properly phased with respect to the anode potential 82, both potentials varying from positive to negative according to the source of alternating current ll. Adjustable contact 25 controls the amplitude of the grid potential 88. Adjustment of the variable resistor 21 may vary the phase of the potential 38 approximately 90 as indicated by the curve 38a. To cause the tube to fire at a particular point along the curve of the anode voltage 82, a shift in phase from 38 toward 88a is required. Where a shift in phase has been effected to the phase condition represented by curve 38b, the tube is caused to fire at a potential such as indicated by the dotted line 38 when the bias 38b becomes more positive than the critical grid bias of the tube as represented by curve 35. This flow of current through the tube ll produces at the cathode connection 39 a sudden rise in potential across. the resistor 88 to ground lead 24, thereby producing a substantially vertical leading edge II for the pulse I8. The trailing edge of the pulse gradually diminishes due to the increased dropping off of the anode potential 82 beyond the line 88.

The tube i2 and the associated network produces in a like manner a second pulse ill for the second half of the alternating current cycle,

Thus, the two tubes. Ii and i2 produce one pulse for ach half cycle of the alternating current applied to the transformer H. The occurrence of these pulses, that is the occurrence of the leading edges 4i thereof may be varied within limits throughout the major portion of the second and fourth quarters of the alternating current cycles.

If desired the pulses i8 may be caused to occur during the first and third quadrants of the cycle by interchanging the condenser 28 with the resistor 21 as will become clear hereinafter from the description of Figs. 4 and 5. Pulses i8 may also be caused to occur during each quadrant of a cycle by combining the circuits of Pig. 1 and Fig. 4. It will also be clear that a. circuit may be provided to produce one pulse per cycle, the occurrence being in any desired quadrant. By additional tube circuits a multiple of pulses may be provided, the pulses occurring at desired points along the period of the alternating current.

Should it be desirable to provide a high speed sweep potential from the pulses II this may be done by providing an outlet connection 88 having a resistor 82 and a condenser 88, the resistor being connected to the lead 88 and the condenser to the ground lead 28. The time constant of this outlet connection increases in duration the pulses I8 similarly as shown at '8 (curve c, Fig. 2). By suitably clipping the expanded pulse 88 at a level 8 I, a substantially linear-inclined sweep 82 is provided. The connection 88 may be taken through a coaxial cable 88 the outer sheath of which is grounded at 88.

The pulses it may be used as low voltage synchronizin or blocking pulses by connecting onto the circuit at 58 through coupling condenser 81.

Before applying the energy of the pulses II to the gas-discharge tube 82, we preferably reshape the pulses by applying some to a differentiating circuit comprising condenser 88 and a resistor 88. This results in a series of narrow positive pulsations 88 each of which is in coincidence substantially with a leading edge ll of the pulses l8. No appreciable negative pulsations are produced by the differentiation because of the gradual slope of the trailing edges of the pulses l8. Further, since only the positive pulsations 88 are applicable as triggering pulses, any negative pulsations produced may be disregarded. These positive pulsations 88 are applied to a negatively-biased gas-discharge tube 82 for the production of high potential pulses.

The tube 82 has an anode 88 connected to the primary 88 of a pulse transformer 88 which may be an air or iron core type, The secondary 81 of the transformer 88 is connected through a coupling condenser 88 and an isolating resistor 89 to an outlet terminal 18. The other end of the secondary 81 is grounded at 12. The primary 88 is connected through a circuit connection having a resistor 18 and a condenser 18 connected in parallel relation to an output connection 11 of a half wave rectifier 88. The rectifier 88 may be of any desired type and as shown may comprise a two electrode tube 8| suitably connected to a transformer 88 the primary 88 of which is connected to the source of alternating current II. The rectifier 88 provides direct current to maintain a condenser 88 fully charged so as to supply an ample amount of energy whenever the tube 82 is rendered conductive by the pulses 88. The tube 82 is provided with a cut-off bias by connecting the grid 88 through resistors 89 and 30 to the negative side of the rectifier ll. The output of the differentiating circuit which provides the pulsations 63 is connected to the grid 83. The cathode 32 of the tube 32 is connected to the ground lead 24 which is also connected through a network of resistors 33 and 94 and a condenser. 35 to the rectifier circuit ll.

- Upon ignition of the tube 32 by the triggering operation of a pulsation 30, energy is discharged from the condenser 36 causing a high peak current pulse to flow through the condenser 13 and the primary 34 of the output transformer 85. This induces a high voltage pulse in the secondary 31 which is applied through the isolating resistor 03 in substantially the form indicated by the .narrowpulse IIIII (curve e) of from about 1 to 2 microseconds more or .less. The resistor II operates as a bleederwhich discharges the condenser I6 before initiation of. a succeeding pulse. The time constant of the combination I! and I8 constitutes the pulse repetition limitation of this circuit while resistor 15 controls the extinction of the tube 82. I

This circuit provides a critically damped or damped oscillatory output pulse which is of high voltage peak amplitude when connected across a high resistance load such as 25,000 ohms or greater. These pulses I0] may be substantially coincident "with the pulsations 80 or made to lag the pulsations 60. This is accomplished by providing an adiustablewcondenser 3| between the grid and ground lead 24. By applying capacity atSI, the leading edges of the triggering pulsations are sloped thereby delaying the triggering action.

Inthe embodiment shown in Fig. 3, we provide a similar circuit for generating the initial pulses I0 by means of twoi-electrode gas-discharge tubes III and 2. These tubes are connected in push-pull arrangement similar to the tubes II and I2 of Fig. 1 with the-exception that the condenser 23 is replaced by capacitance I23. A selected capacitance I23 together with the adjusted voltage-at contact 23 provide for variation of the phase angle of the control circuit voltage on the grid 1230f the tube III. This variation may be a dropping resistance 2" and a coupling condenser 201. The operation of this circuit comprises the triggering of the power amplifier tube I32 operating to connect the high voltage charge on the condenser 20! through resistor 20' and condenser 20'! across the output terminal I10 and ground. The output pulse is preferably critically damped so that substantially no trailing oscillations are produced after the initial pume.

Where this high potential pulse is used for synchronizing the operation ,of the spark discharge type modulator disclosed in the aforesaid copending application of Labin and Ostlund, the synchronizing pulse voltage is applied to a spark gap of the spark generator thereof.

Referring to Figs. .4 and 5, still another embodiment of the invention similar to the embodiment shown in Fig. 1 is illustrated arranged to use alternating current instead of direct current as the stored energy for production of the high voltage pulses. Inthis embodiment no rectifiers are used. Since the circuit of Fig. 4 is in part identical with parts of the circuit of Fig. "1, only those portions differing therefrom need be described. 1

The initial pulse 2I0 is produced from the alternating current source applied through transformer 2I3 to two gas-discharge tubes 2 and 2I2. The circuit of this portion of thecircuit is identical to the corresponding portion of Fig. 1 with the exception that the relation of the resister 21 and the condenser 23 of the phaseishifting circuit is reversed as indicated by the resistor I2'I andcondenser I23 relation shown ingFig. 4.

.Also the movable contacts for R2 and R4 are interchanged so that the contact 223 is now associated with the resistor R2 instead of the resistor R4.

' This provide a phase lagging positive bias for accomplished by making the resistor I2'I variable as in the case-of resistor 21, Fig. 1. The cathode resistor I63 is connected to the common cathode lead of the tubes III and H2 and to the ground lead I24. I

This circuit (Fig. 3) may be provided. with a sweep potential outlet I" and a synchronizing pulse outlet I 53 similarly as in the case of the system of Fig. l. Pulsations 80 are produced by the diflerentlating circuit I40, I33.

The grid connection I3! is tapped by an adiustable contact to a resistor I9II connected across the rectifier I30.

Asecond rectifier 202 is provided in association with a high voltage transformer I. A condenser 23' is maintained fully charged by the rectifier 202 and one side thereof is connected to the anode III of the tube I32 while the other side thereof is connected to an output terminal I" through the tube 2I I during the positive half of the alternating current cycle indicated by the voltage curve 232. By adjusting the contact 223, a phase shift can be effected causing the biasing 'grid voltage 230 for the. tube 2 to lag the applied anode voltage 232. By adjusting the contact 223, the phase shift of the biasing voltage 230 may be varied for approximately the of the first quadrant of the cycle represented by the curve 232. The tube 2 has a characteristic critical bias 233 which when crossed by the curve 233 will cause the tube to fire thereby producing an abrupt increase in potential on the cathode connection 233 as represented by. the vertical leading edge 2 of the pulse 2III (curve b, Fig. 5). The conduction continues for substantially the remaining portionof the positive half cycle of curve 232 producing the curved trailing portion of the pulse 2IlI.

Outlets 2 and 253 are provided for the purpose of furnishing a sweep voltage and synchronizing pulses of low voltage similarly as in the case of Figs-i and 3.

The pulses 2III from the tubes 2 and 2I2 are differentiated by the circuit including the condenser 246, the resistor 289 and Rs thereby producing anarrow pulsation 230 in substantial coincidence with the leading edge 2. The pulsationflll is applied through a resistor 233 and a condenser 23I for re-shaplng as indicated by the pulse .shape 230a. This re-shaping preferably slopes the leading edge of the pulse so that the triggering of the tube 262 may be delayed with respect to leading edge of synchronizing pulse 230. The degree of re shaping may be controlled by adJusting the condenser 23L The energy supplied for the anode circuit of the tube 2'2 is provided by a transformer 2". The mid-tap of the transformer 2|. is connected to the ground bus 224. Load resistors Rs and Rs are provided between the terminal 2" of the secondary and the bus 224. Likewise, load resistors R4 and Rs are connected between the opposite transformer terminal 2'2 and the bus 224. Rs. Re and R1, Rs operate as voltage dividers and supply cut-oi! A. C. bias voltage to tubes 2" and 202 respectively. Connected in parallel with these resistors are two condensers Cl and C: to provide a low impedance supply of energy.

It will be noted that an additional high voltage generating tube 283 is provided which is associ-' ated with the portion of the transformer 20. opposite the portion which supplies energy to the tube 2'2. This arrangement of the tubes 202 and 283 provides for the discharge of high voltage pulses in the first and third quadrants of the voltage supply cycle in response to the pulses 2i. produced by the tubes 2 and 2". The anode circuits of the tubes 282 and 2" are each similar to the arrangement of the anode circuit for the tube '2 of Fig. 1. Each anode circuit is provided with a primary winding 2 of a pulse transformer 2". The secondary 281 is responsive to the pulsations produced in the anode circuits so as to provide an output of high voltage pulses 2".

In operation of the circuit, it is desirable to have the voltage supply for the condensers C1 and C: at substantially maximum when the tubes 282 and 283 are triggered. This is obtained by providing a condenser C: in the primary circuit of the transformer 280. This capacitance togather with the load resistance provided by Ra, Ra. R7 and Rs across the secondary produces a leading voltage such as indicated by the curve 2" curve a. This leading voltage is preferably arranged so that the maximum will occur at about the instantsthe tubes 282 and 253 are caused to fire. It will be noted that the tubes 262 and 2" are provided with opposite bias by the grid connections 282 and 293 through the resistors Rs and Rs respectively, to insure the tubes against firing in the absence of pulses 2".

The low impedance source of energy provided by the condensers C1 and enables the tubes :82 and 263 when fired to produce high voltage pulsations resulting in pulses 2". As shown for example by the curve c of Fig. 5, the pulses 2 may be damped oscillations instead of critically damped pulses such as pulses ill.

While we have shown Fig. 4 as comprising circult portions for firing in the first and third quadrants of the alternating current cycle, it will be understood that the circuit may be reduced to provide one pulse per cycle. By combining the circuit of Fig. 4 with a circuit similar to Fig. 1, high voltage pulses may be produced for each quadrant of the alternating current cycle, and by the addition of other such circuits a greater number of pulses per cycle may be produced.

While we have disclosed the principles of our invention in connection with several specific embodiments, it will be understood that the illustrations and descriptions are given by way of example only and not as limiting the scope of the invention as set forth in the objects and the appended claims.

We claim:

1. A system for generating pulses from a source of altematlng current comprising a. gas-discharge tube having anode, cathode and grid electrodes. means to apply alternating voltage from said alternating current source to the anode and grid electrodes, means to control the phase of the alternating voltage applied to one of said electrodes with respect to that applied the other electrode so as to determine the point along the period of the alternating current source at which the tube is rendered conductive, the tube being extinguished by a decrease of the alternating voltage at one of the electrodes, whereby a pulse is produced having a substantially vertical leading edge, means to differentiate the pulse to produce a pulsation of short duration substantially coincident with said leading edge, means including a transformer and condenser arrangement to supply alternating current energy from said source of alternating current, and control means coupled to said last named means operative in response to said pulsation to conduct said alternating current energy for production of a high potential pulse.

2. The system defined in claim 1 wherein said control means comprises an electron tube having a grid connected to the output side of the diiferentiating means and means receiving alternating current energy from said source of alternating current to provide a cut-on bias on said tube.

3. The system defined in claim 1 wherein said control means comprises a pair of electron tubes each having a grid connected to the output side of the differentiating means, and each said tube have a transformer winding and condenser arrangement in its anode circuit, and transformer means for supplying energy to said anode circuits from said alternating current source.

4. The system defined in claim 1 wherein said control means comprises an electron tube having an anode, said transformer having its primary connected in circuit with said anode, means to transmit said pulsation to said electron tube, the means to supply energy being so coupled that when the tube is triggered by said pulsation said energy is conducted through said transformer thereby producing a high potential pulse in the secondary thereof.

5. The system defined in claim 1 wherein said control means comprises an electron tube having an anode together with a condenser, said transformer having the primary thereof connected in circuit with said anode and said condenser, means to transmit said pulsation to said electron tube, the means to supply energy being so coupled that when the tube is triggered by said pulsation said energy is conducted through said transformer thereby producing a high potential pulse in the secondary thereof, said condenser being arranged in said circuit to control the duration of the flow of current producing the high potential pulse.

6. A system for generating pulses of high potential from a source of alternating current comprising means to produce from the alternating current source a low potential pulse having a substantially vertical leading edge, means to differentiate the low voltage pulse to produce a pulsation of short duration substantially coincident with said leading edge, means to supply alternating current energy from said source of alternating current comprising a capacitance arranged to receive alternating current from said source, means operative in response to said pulsation to conduct said energy for production of a high potential pulse, and means to shift the phase of the energy applied to said capacitance so that a maximum supply is timed for the cmduction produced in rsponse to said pulsation.

7. The system defined in claim 6 wherein the 9 means operative in response to said pulsation comprises a grid controlled electron tube having an anode, a transformer having the primary thereof connected to said anode and to the means to supply energy so that when said tube is triggered by said pulsation, current is caused to flow through said primary thereby producing a high potential in the secondary of the transformer.

EVER'I MANUEL OS'I'LUND. PAUL W. SOKOLOFF.

REFERENCES CITED The following references are of record in the file of this patent:

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